What is Berel Jastrow's job at Auschwitz in the novel, War and Remembrance?

Berel is put first on a building crew that is in charge of the first crematorium at Auschwitz. Later, he is assigned grave duty. His job is to pick up the corpses of the many Jews who were killed and buried in mass graves. All are then searched for valuables and put on giant pyres to be burned.